This invention relates to a small, hand-held apparatus for agitating liquid solutions or suspensions. In accordance with another aspect, this invention relates to an electrically operated agitating apparatus. In accordance with a further aspect, this invention relates to an agitating apparatus having a disposable hollow mixing shaft made of a polymer material.
In some fields of science and commerce there has been a growing trend to conduct analytical analysis, physical mixing or stirred chemical or biochemical reactions in smaller vessels such as test-tubes, cups or cuvettes. Such vessels typically hold from 0.1 to 50 mL of liquid. This is done to conserve valuable materials and to minimize the laboratory space needed to conduct analysis, mixing or reactions. Such a trend also receives emphasis from the fact that the sample size required by many analytical instruments has become much smaller than a few decades ago. As smaller vessels are used, it has become necessary to find smaller pieces of equipment to achieve mixing in these vessels. A logical answer is to scale down manually and electrically driven mixers. Such stirrers known in the art are described in the catalogs of instrument supply companies. Despite the claim to being small or ministirrers, some are still too large to be used in small vessels such as test-tubes, sample cups cuvettes and beakers.
Furthermore, the present art does not address some unique problems encountered in using small mixing vessels holding from 0.1 to 50 mL liquid. Such vessels often have narrow necks and stirring shafts rigidly attached to motor drives are difficult to align to avoid vessel damage or spillage. Sill further, because the agitating shaft is permanently mounted to the drive motor, it is necessary to clean or wipe the drive shaft between samples when working with multiple samples. Cross-contamination can be a serious problem and it would be desirable to use a new sanitized agitator shaft for each sample. Finally, it is desirable in many stirring operations using test-tubes to disperse and resuspend a fine and sometimes sticky solid mass obtained by previous centrifugation of a solid-liquid suspension. The centrifuged solid mass rests in the bottom of a centrifuge test tube and must be mechanically loosened from the bottom and broken up with a stirring device. Using the presently available electrically driven stirrers cited above, one cannot accomplish a mechanical loosening and breakage without risk of damage to the test tube, stirring apparatus or operator.